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Pregnancy may be risk factor for late-onset post-LASIK ectasia
Cases have been reported up to 9 years after refractive surgery, once the patient became pregnant.
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Pregnancy may trigger late-onset keratectasia up to 9 years after LASIK surgery, according to a cornea specialist.
“Pregnancy may be a potential additional risk factor to keep in mind when we do preoperative patient screening for laser refractive surgery using the Ectasia Risk Score System,” Farhad Hafezi, MD, PhD, said at the joint meeting of Refractive.online and SICCSO in Rome.
Considering pregnancy as a potential risk factor when assessing candidates for LASIK might be important, he said. This risk should be included in the benefit-risk analysis prior to LASIK in borderline cases, and borderline cases should be even more carefully identified preoperatively if they are young women.
“What I have implemented in my practice is that if I have a borderline case who is a young woman who wishes to become pregnant within a few years, I prefer not to offer LASIK,” he said.
The first case of a patient who developed ectasia 1 month after LASIK surgery was published by Seiler in 1998, raising awareness that an alteration of corneal biomechanics might occur with the ablation of tissue and cause irreversible damage. The need to establish limits to the depth of ablation and leave enough residual stromal bed to maintain corneal strength was recognized. A residual thickness of 250 µm was considered adequate for safe ablation.
Farhad Hafezi
“With time, we developed better preoperative screening methods and learned more about the posterior surface of the cornea. Consensus was achieved on not treating patients with thin corneas,” Hafezi said. “Over the years, however, there was an explosion of reports on iatrogenic ectasia. We know now that ectasia can occur with a residual bed of 300 µm, that it can occur after PRK and not only after LASIK, and that there is more to biomechanics than thickness alone. It is also the way the collagen fibers interconnect and interweave, the temporal and spatial distribution of cross-links.”
Effect of estrogen
There are factors that temporarily modify corneal biomechanics, one of which is estrogen, Hafezi said. In 2001, Suzuki and colleagues showed that there are receptors for estrogen in the human cornea and that they upregulate collagenases via prostaglandin release. Experimental studies by Spoerl and colleagues showed that estrogens heavily decrease corneal biomechanics in vitro compared to controls.
There is also an increasing number of reports showing pregnancy-related exacerbation of keratoconus or iatrogenic ectasia.
“No wonder, since during pregnancy, estrogen increases by a factor of 30,000,” Hafezi said.
The first case that he encountered was a 33-year-old woman treated with LASIK in 2000. Preoperatively, she had 5 D of myopia and 0.5 D of astigmatism and 20/20 best corrected visual acuity in both eyes. Topography was normal.
After LASIK, she had 20/20 uncorrected visual acuity, which was stable for 2 years.
“Decompensation with significant loss of vision suddenly occurred during her first pregnancy. She was cross-linked, and over the following 2 years, she was not only stable, but had a significant reduction in [keratometry] readings. But in 2007, she had a second pregnancy and ectasia developed again,” Hafezi said.
Role of pregnancy
A retrospective case series of five women with progressive iatrogenic ectasia during pregnancy by Hafezi and colleagues was published in 2012. All patients had previously undergone LASIK, and their corneas had been stable for years.
“They were pregnant at various intervals, from 2 years to 9 years after corneal refractive surgery. All of them started decompensating during pregnancy,” Hafezi said. “The main conclusion is that pregnancy may trigger late-onset keratectasia up to 9 years after LASIK.”
While no abnormal sign was seen on topography in any of these women, Hafezi said he cannot rule out that they might have been compensated borderline cases, stable until an additional factor — the increased estrogen level — arose with pregnancy.
Data on the physiology of pregnancy and its influence on corneal biomechanics are needed, he said.
“We have started this research in Geneva. We are comparing estrogen levels of women throughout their pregnancy and seeing their effects on corneal biomechanics through topography and biomechanical measurements,” Hafezi said. “We are also evaluating the effects of thyroid hormones, because thyroxin has a major influence on biomechanics.” – by Michela Cimberle